Plasma processing apparatus and heater temperature control method

ABSTRACT

A plasma processing apparatus is provided that converts a gas into plasma using a high frequency power and performs a plasma process on a workpiece using an action of the plasma. The plasma processing apparatus includes a processing chamber that can be depressurized, a mounting table that is arranged within the processing chamber and holds the workpiece, an electrostatic chuck that is arranged on the mounting table and electrostatically attracts the workpiece by applying a voltage to a chuck electrode, a heater arranged within or near the electrostatic chuck, and a temperature control unit. The heater is divided into a circular center zone, at least two middle zones arranged concentrically at an outer periphery side of the center zone, and an edge zone arranged concentrically at an outermost periphery. The temperature control unit adjusts a control temperature of the heater with respect to each of the zones.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional application and claims priorityunder 35 U.S.C. 120 to U.S. patent application Ser. No. 14/368,548,filed on Jun. 25, 2014, which is the National Stage of InternationalApplication No. PCT/JP2013/050195, filed on Jan. 9, 2013, which claimspriority under 35 U.S.C. 119 to Japanese Patent Application No.2012-005590, filed on Jan. 13, 2012 and U.S. Patent Application No.61/587,706, filed on Jan. 18, 2012. The entire contents of the foregoingapplications are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a plasma processing apparatus and aheater temperature control method.

BACKGROUND ART

Temperature control of a workpiece placed on a mounting table isindispensable for controlling an etching rate, for example. Temperaturecontrol affects the uniformity of a plasma process performed on theworkpiece and is therefore an important aspect of the plasma process.

An electrostatic chuck (ESC) that electrostatically attracts theworkpiece by applying a voltage to a chuck electrode is arranged on themounting table. In recent years, heater embedded electrostatic chuckmechanisms have been proposed that have heaters embedded within theelectrostatic chuck such that the surface temperature of theelectrostatic chuck may be rapidly changed through heat generation bythe heaters. For example, Patent Document 1 discloses a temperaturecontrol technique implemented by a heater embedded electrostatic chuckmechanism. According to Patent Document 1, heaters arranged in theheater embedded electrostatic chuck mechanism are divided into two zonesincluding a circular center zone and an edge zone that is concentricallyarranged around the outer periphery of the center zone, and temperaturecontrol is implemented with respect to each of these zones.

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: Japanese Laid-Open Patent Publication No.    2008-85329

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, in the above temperature control method that divides heatersinto two zones, the heater area of one zone is still relatively largesuch that unevenness may be created in the temperature distributionwithin the same zone even when temperature control is implemented withrespect to each zone. As a result, uniformity in the etching rate andthe etching shape may not be achieved. Etching characteristics areparticularly degraded at a boundary portion between the center zone andthe edge zone.

In light of the above, one aspect of the present invention relates toproviding a plasma processing apparatus and a heater temperature controlmethod that are capable of dividing a heater arranged within or near anelectrostatic chuck into at least four zones and implementingtemperature control with respect to each of these zones.

Means For Solving the Problem

According to one embodiment of the present invention, a plasmaprocessing apparatus is provided that is configured to convert a gasinto plasma using a high frequency power and perform a plasma process ona workpiece using an action of the plasma. The plasma processingapparatus includes a processing chamber that can be depressurized, amounting table that is arranged within the processing chamber and isconfigured to hold the workpiece, an electrostatic chuck that isarranged on the mounting table and is configured to electrostaticallyattract the workpiece by applying a voltage to a chuck electrode, aheater arranged within or near the electrostatic chuck, and atemperature control unit. The heater is divided into a plurality ofzones including a circular center zone, at least two middle zonesarranged concentrically at an outer periphery side of the center zone,and an edge zone arranged concentrically at an outermost periphery. Thetemperature control unit is configured to adjust a control temperatureof the heater with respect to each of the plurality of zones.

According to another embodiment of the present invention, a heatertemperature control method is provided for controlling a temperature ofa heater arranged in a plasma processing apparatus, which is configuredto convert a gas into plasma using a high frequency power and perform aplasma process on a workpiece using an action of the plasma. The plasmaprocessing apparatus includes a processing chamber that can bedepressurized, a mounting table that is arranged within the processingchamber and is configured to hold the workpiece, an electrostatic chuckthat is arranged on the mounting table and is configured toelectrostatically attract the workpiece by applying a voltage to a chuckelectrode, a heater arranged within or near the electrostatic chuck, anda storage unit. The heater is divided into a plurality of zonesincluding a circular center zone, at least two middle zones arrangedconcentrically at an outer periphery side of the center zone, and anedge zone arranged concentrically at an outermost periphery. The storageunit stores in advance a correlation between a setting temperature ofeach of the zones and a current value to be applied to the heater tocontrol the heater to a control temperature of each of the zones, thecontrol temperature being obtained by correcting a deviation of asurface temperature of the electrostatic chuck with respect to thesetting temperature of each of the zones and correcting a temperatureinterference from an adjacent zone with respect to the settingtemperature of each of the zones. The heater temperature control methodincludes the steps of acquiring a temperature detected by a temperaturesensor arranged in at least one zone of the plurality of zones andsetting up the acquired temperature as a setting temperature of the atleast one zone, calculating a current value to be applied to the heaterof each of the zones based on the acquired setting temperature of the atleast one zone and the correlation stored in the storage unit, andcontrolling the temperature of the heater of each of the zones byapplying the calculated current value to the heater of each of thezones.

Advantageous Effect of the Invention

According to an aspect of the present invention, a heater arrangedwithin or near an electrostatic chuck may be divided into at least fourzones and temperature control may be implemented with respect to each ofthese zones.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an overall configuration of a plasma processingapparatus according to an embodiment of the present invention;

FIG. 2 is an enlarged view of a heater embedded electrostatic chuckmechanism of FIG. 1 including a heater arranged near an electrostaticchuck;

FIG. 3 is an enlarged view of a heater embedded electrostatic chuckmechanism including a heater arranged within an electrostatic chuckaccording to a first modified embodiment;

FIG. 4 is an enlarged view of a heater embedded electrostatic chuckmechanism including a heater arranged near an electrostatic chuckaccording to a second modified embodiment;

FIG. 5 illustrates exemplary process steps that may be performed by theplasma processing apparatus according to an embodiment of the presentinvention;

FIG. 6 illustrates process results of implementing temperature controlwhen a heater is divided into two zones;

FIG. 7 illustrates process results of implementing temperature controlwhen the heater is divided into two zones and when the heater is dividedinto four zones;

FIG. 8 illustrates process results of implementing temperature controlwhen the heater is divided into two zones and when the heater is dividedinto four zones;

FIG. 9 illustrates an exemplary arrangement of the areas of the zonesand power switching at the zones of the heater according to anembodiment of the present invention;

FIG. 10 illustrates another exemplary arrangement of the areas of thezones and power switching at the zones of the heater according to anembodiment of the present invention;

FIG. 11 illustrates an arrangement of the zones of the heater and atemperature sensor according to an embodiment of the present invention;

FIG. 12 illustrates another arrangement of the zones of the heater andtemperature sensors according to an embodiment of the present invention;

FIG. 13 illustrates a functional configuration of a control deviceaccording to an embodiment of the present invention;

FIG. 14 illustrates a method of calculating correction values α₁ and β₁with respect to a heater setting temperature Y₁ according to anembodiment of the present invention;

FIG. 15 illustrates a method of calculating correction values α₂ and β₂with respect to a heater setting temperature Y₂ according to anembodiment of the present invention;

FIG. 16 illustrates a method of calculating correction values α₃ and β₃with respect to a heater setting temperature Y₃ according to anembodiment of the present invention;

FIG. 17 illustrates a method of calculating correction values α₄ and β₄with respect to a heater setting temperature Y₄ according to anembodiment of the present invention;

FIG. 18 illustrates corrections implemented with respect to the settingtemperatures of the zones and corresponding input current values to beapplied to the zones; and

FIG. 19 is a flowchart illustrating process steps of a temperaturecontrol process according to an embodiment of the present invention.

EMBODIMENTS FOR IMPLEMENTING THE INVENTION

In the following, embodiments of the present invention are describedwith reference to the accompanying drawings. Note that elements havingsubstantially the same functions or features may be given the samereference numerals and overlapping descriptions thereof may be omitted.

[Overall Configuration of Plasma Processing Apparatus]

First, an overall configuration of a plasma processing apparatusaccording to an embodiment of the present invention is described withreference to FIG. 1. The plasma processing apparatus 1 illustrated inFIG. 1 is configured as a dual frequency capacitively coupled plasmaetching apparatus. The plasma processing apparatus 1 includes acylindrical vacuum chamber (processing chamber) 10 (simply referred toas “chamber” hereinafter) made of aluminum having an alumite-treated(anodized) surface, for example. The chamber 10 may be grounded, forexample.

A mounting table 12 configured to hold a semiconductor wafer W(hereinafter, simply referred to as a “wafer W”) thereon as a workpieceis arranged within the chamber 10. The mounting table 12 may be made ofaluminum, for example, and is supported on a cylindrical support 16 viaan insulating cylindrical holder 14. The cylindrical support 16 extendsvertically upward from a bottom of the chamber 10. To improve in-planeetching uniformity, a focus ring 18 that may be made of silicon, forexample, is arranged on a top surface of the mounting table 12 tosurround the outer edge of an electrostatic chuck 40.

An exhaust path 20 is formed between a sidewall of the chamber 10 andthe cylindrical support 16. A ring-shaped baffle plate 22 is arranged inthe exhaust path 20. An exhaust port 24 is formed at a bottom portion ofthe exhaust path 20 and is connected to an exhaust device 28 via anexhaust pipe 26. The exhaust device 28 includes a vacuum pump (notshown) and is configured to depressurize a processing space within thechamber 10 to a predetermined vacuum level. A gate valve 30 configuredto open/close an entry/exit port for the wafer W is provided at thesidewall of the chamber 10.

A first high frequency power supply 31 for drawing ions and a secondhigh frequency power supply 32 for plasma generation are electricallyconnected to the mounting table 12 via a matching unit 33 and a matchingunit 34, respectively. The first high frequency power supply 31 may beconfigured to apply to the mounting table 12 a first high frequencypower of a relatively low frequency (e.g. 0.8 MHz) that is suitable fordrawing ions from within the plasma onto the wafer W placed on themounting table 12. The second high frequency power supply 32 may beconfigured to apply to the mounting table 12 a second high frequencypower of a higher frequency (e.g. 60 MHz) that is suitable forgenerating a plasma within the chamber 10. In this way, the mountingtable 12 also acts as a lower electrode. Further, a shower head 38,which is described below, is provided at a ceiling portion of thechamber 10. The shower head 38 acts as an upper electrode at a groundpotential. In this way, the second high frequency power from the secondhigh frequency power supply 32 is capacitively applied between themounting table 12 and the shower head 38.

The electrostatic chuck 40 configured to hold the wafer W by anelectrostatic attractive force is provided on the top surface of themounting table 12. The electrostatic chuck 40 includes an electrode 40 athat is made of a conductive film and is arranged between a pair ofinsulating layers 40 b (see FIGS. 2-4) or insulating sheets. A DCvoltage supply 42 is electrically connected to the electrode 40 a via aswitch 43. The electrostatic chuck 40 electrostatically attracts andholds the wafer W by a Coulomb force that is generated when a voltage isapplied thereto from the DC voltage supply 42.

A heat transfer gas supply source 52 is configured to supply a heattransfer gas such as He gas between the backside surface of the wafer Wand the top surface of the electrostatic chuck 40 through a gas supplyline 54.

The shower head 38 disposed at the ceiling portion of the chamber 10includes an electrode plate 56 having multiple gas holes 56 a and anelectrode supporting body 58 configured to detachably hold the electrodeplate 56. A gas supply source 62 supplies gas to the shower head 38 viaa gas supply pipe 64, which is connected to a gas inlet 60 a. In thisway, the gas may be introduced into the chamber 10 from the multiple gasholes 56 a.

A magnet 66 is arranged to extend annularly or concentrically around thechamber 10 so that the plasma generated within a plasma generation spaceof the chamber 10 may be controlled by the magnetic force of the magnet66.

A coolant path 70 is formed within the mounting table 12. A coolantcooled to a predetermined temperature is supplied to the coolant path 70from a chiller unit 71 via pipes 72 and 73. Also, a heater 75 that isdivided into four zones is attached to the backside surface of theelectrostatic chuck 40. Note that the configuration of the heater 75 isdescribed in detail below. A desired AC voltage is applied to the heater75 from an AC power supply 44. In this way, the temperature of the waferW may be adjusted to a desired temperature through cooling by thechiller unit 71 and heating by the heater 75. Note that such temperaturecontrol may be performed based on a command from a control device 80.

The control device 80 is configured to control the individual componentsof the plasma processing apparatus 1 such as the exhaust device 28, theAC power supply 44, the DC voltage supply 42, the switch 43 for theelectrostatic chuck, the first high frequency power supply 31, thesecond high frequency power supply 32, the matching units 33 and 34, theheat transfer gas supply source 52, the gas supply source 62, and thechiller unit 71. The control device 80 also acquires a sensortemperature detected by a temperature sensor 77 attached to the backsidesurface of the heater 75. Note that the control device 80 may beconnected to a host computer (not shown).

The control device 80 includes a CPU (Central Processing Unit), a ROM(Read Only Memory), and a RAM (Random Access Memory), which are notshown. The CPU executes a plasma process according to various recipesstored in a storage unit 83 illustrated in FIG. 13, for example. Thestorage unit 83 storing the recipes may be configured as a RAM or a ROMusing a semiconductor memory, a magnetic disk, or an optical disk, forexample. The recipes may be stored in a storage medium and loaded in thestorage unit 83 via a driver, for example. Alternatively, the recipesmay be downloaded from a network (not shown) and stored in the storageunit 83, for example. Also, note that a DSP (digital signal processor)may be used instead of the CPU to perform the above functions. Thefunctions of the control device 80 may be implemented by software,hardware, or a combination thereof.

When performing an etching process using the plasma processing apparatus1 having the above-described configuration, first, the gate valve 30 isopened, and a wafer W that is held by a transfer aria is loaded into thechamber 10. Then, the wafer W is lifted from the transfer aim by pusherpins (not shown), and the wafer W is placed on the electrostatic chuck40 when the pusher pins are lowered. After the wafer W is loaded, thegate valve 30 is closed. Then, an etching gas is introduced into thechamber 10 from the gas supply source 62 at a predetermined flow rateand flow rate ratio, and the internal pressure of the chamber 10 isreduced to a predetermined pressure by the exhaust device 28. Further,high frequency powers at predetermined power levels are supplied to themounting table 12 from the first high frequency power supply 31 and thesecond high frequency power supply 32. Also, a voltage from the DCvoltage supply 42 is applied to the electrode 40 a of the electrostaticchuck 40 so that the wafer W may be fixed to the electrostatic chuck 40.A heat transfer gas from the heat transfer gas supply source 52 issupplied between the top surface of the electrostatic chuck 40 and thebackside surface of the wafer W. Etching gas sprayed into the chamber 10from the shower head 38 is excited into a plasma by the first highfrequency power from the first high frequency power supply 32. In thisway, the plasma is generated within the plasma generation space betweenthe upper electrode (shower head 38) and the lower electrode (mountingtable 12), and a main surface of the wafer W is etched by ions andradicals included in the generated plasma. Also, the ions in the plasmamay be drawn toward the wafer W by the first high frequency power fromthe first high frequency power supply 31.

After plasma etching is completed, the wafer W is lifted and held by thepusher pins, the gate valve 30 is opened, and the transfer arm isintroduced into the chamber 10. Then, the pusher pins are lowered sothat the wafer W may be held by the transfer arm. Then, the transfer armexits the chamber 10, and a next wafer W is loaded into the chamber 10by the transfer arm. By repeating the above-described procedures, wafersW may be successively processed.

(Heater Configuration)

In the following, the configuration of the heater 75 is described indetail with reference to FIG. 2. FIG. 2 is an enlarged view of themounting table 12 and the electrostatic chuck 40 illustrated in FIG. 1.In FIG. 2, the heater 75 is attached to the backside surface of theelectrostatic chuck 40. However, in other embodiments, the heater 75 maybe arranged within or near the electrostatic chuck 40. For example, inFIG. 3, the heater 75 is embedded within the insulating layer 40 b ofthe electrostatic chuck 40.

The heater 75 is divided into a circular center zone A, two middle zones(inner middle zone B and outer middle zone C) arranged concentricallyaround the outer periphery side of the center zone A, and an edge zone Darranged concentrically around the outermost periphery (see FIGS. 11 and12). Note that although the middle zones are divided into two zones inthe present embodiment, the middle zones may also be divided into threeor more zones, for example. Particularly, in a case where the diameterof the wafer W is greater than or equal to 450 mm, the middle zones ofthe heater 75 are preferably divided into at least three zones in orderto achieve higher temperature controllability at the middle zones.

The electrostatic chuck 40 and the mounting table 12 may be attached toone another by an adhesive, for example. In this way, the heater 75attached to the electrostatic chuck 40 may be embedded within anadhesive layer 74 and fixed between the electrostatic chuck 40 and themounting table 12. In the case where the heater 75 is attached to thebackside surface of the electrostatic chuck 40 as illustrated in FIG. 2,the arrangement of the heater 75 (heater pattern) may be freely altereduntil right before the electrostatic chuck 40 and the mounting table 12are bound together by the adhesive layer 74. Also, even after theelectrostatic chuck 40 and the mounting table 12 are bound together bythe adhesive layer 74, the heater pattern may still be altered bydetaching the electrostatic chuck 40 and the mounting table 12, alteringthe heater pattern as desired, reapplying an adhesive on the heater 75,and reattaching the electrostatic chuck 40 and the mounting table 12together.

On the other hand, in the case where the heater 75 is embedded withinthe electrostatic chuck 40, the heater 75 is fixed within the insulatinglayer 40 b when the insulating layer 40 b is sintered. In this case, theheater pattern may not be altered after the heater 75 is embedded withinthe insulating layer 40 b. Thus, in a case where the heater 75 isdivided into four or more zones such that the heater pattern becomesrather complicated as in the present embodiment, a heater configurationenabling easy rearrangement of the heater pattern such as thatillustrated in FIG. 2 is preferably used rather than the heaterconfiguration having the heater 75 embedded within the electrostaticchuck 40 as illustrated in FIG. 3.

Also, in the case where the heater 75 is attached to the backsidesurface of the electrostatic chuck 40 as illustrated in FIG. 2, theheater 75 is embedded in the adhesive layer 74. Note that when theheater 75 is embedded in the insulating layer 40 b as illustrated inFIG. 3, the heater 75 may not be arranged near the edge portions of theelectrostatic chuck 40 because thin ceramic portions of the insulatinglayer 40 b may break when the insulating layer 40 b is sintered.However, such constraints are not imposed on the heater 75 that isembedded in the adhesive layer 74 as illustrated in FIG. 2. Thus, theheater 75 may be arranged to extend near the edge portions of theelectrostatic chuck 40 in FIG. 2. As a result, the temperature of theelectrostatic chuck 40 may be uniformly controlled up to its outermostedge portions in the heater configuration of FIG. 2 where the heater 75is attached to the backside surface of the electrostatic chuck 40.

Note that in some embodiments, the coolant path 70 arranged opposite theheater 75 may be arranged into a pattern corresponding to the zones ofthe heater 75 as illustrated in FIG. 4, for example. In this way,temperature controllability and responsiveness may be improved by thecooling by the coolant flowing in the coolant path 70 arranged accordingto the zones of the heater 75 and heating by the heater 75.

(Plasma Process)

The configurations of the plasma apparatus 1 and the heater 75 accordingto the present embodiment have been described above. In the following,an exemplary plasma process that may be implemented by the plasmaprocessing apparatus 1 according to the present embodiment are describedwith reference to FIG. 5.

FIG. 5 illustrates exemplary process steps of the plasma process thatmay be implemented by the plasma processing apparatus 1 of the presentembodiment. Note that in the following description of the process steps,setting temperatures of a heater divided into two zones (centeredge)corresponding to a comparison example are indicated as exemplary heatertemperature control conditions corresponding to one of the processconditions of the plasma process.

In S1 of FIG. 5, a silicon oxide (SiO₂) film 108 having a siliconnitride (SiN) film 106, an amorphous silicon (α-Si) film 104, ananti-reflection (BARC: bottom anti-reflective coating) film 102, and aphotoresist film 100 stacked thereon in this order is illustrated. Thesilicon oxide film 108 corresponds to an interlayer insulating filmformed by CVD (chemical vapor deposition) using TEOS(tetraethoxysilane).

The BARC (anti-reflection) film 102 may be formed on the amorphoussilicon (α-Si) film 104 by a coating process, for example. The BARC film102 is made of a polymer resin containing a pigment that absorbs lighthaving a specific wavelength such as ArF excimer laser light that isirradiated toward the photoresist film 100, for example. The BARC film102 prevents the ArF excimer laser light that has passed through thephotoresist film 100 from being reflected back to the photoresist film100 by the amorphous silicon film 104. The photoresist film 100 may beformed on the BARC film 102 using a spin coater (not shown), forexample. The photoresist film 100 has a pattern (resist pattern) foamedthereon including openings arranged at positions where predeterminedholes are to be formed.

Referring to S2 of FIG. 5, first, the BARC film 102 is etched using thephotoresist film 100 as a mask. In this way, the openings of the resistpattern are transferred to the BARC film 102. As process conditions forthis process step, a pressure of 5 (mTorr) is prescribed, the secondhigh frequency power/first high frequency power are prescribed to be200/50 (W), a gas containing CF₄/O₂ is prescribed, and settingtemperatures of the heater are prescribed to be center/edge=60/50° C.

Next, referring to S3 of FIG. 5, the amorphous silicon film 104 isetched using the photoresist film 100 and the BARC film 102 as masks. Inthis way, the pattern of the BARC film 102 may be transferred to theamorphous silicon film 104. As process conditions for this process step,a pressure of 25 (mTorr) is prescribed, the second high frequencypower/first high frequency power are prescribed to be 200/100 (W), a gascontaining HBr is prescribed, and setting temperatures of the heater areprescribed to be center/edge=50/40° C.

Next, referring to S4 of FIG. 5, O₂ asking is performed and thephotoresist film 100 and the BARC film 102 are removed. As processconditions for this process step, a pressure of 50 (mTorr) isprescribed, the second high frequency power/first high frequency powerare prescribed to be 750/0 (W), a gas containing O₂ is prescribed, andsetting temperatures of the heater are prescribed to becenter/edge=50/40° C.

Next, referring to S5 of FIG. 5, the silicon nitride film 106 is etchedusing the amorphous silicon film 104 as a mask (main etching). In thisway, the pattern of the amorphous silicon film 104 may be transferred tothe silicon nitride film 106. As process conditions for this processstep, a pressure of 20 (mTorr) is prescribed, the second high frequencypower/first high frequency power are prescribed to be 400/300 (W), a gascontaining CH₂F₂/CH₃F/O₂ is prescribed, and setting temperatures of theheater are prescribed to be center/edge=35/35° C.

Next, referring to S6 of FIG. 5, the silicon oxide film 108 is etchedusing the amorphous silicon film 104 and the silicon nitride film 106 asmasks (over etching). Note that a portion of the silicon nitride film106 remains on the silicon oxide film 108 when this process step isperformed. As process conditions for this process step, a pressure of 20(mTorr) is prescribed, the second high frequency power/first highfrequency power are prescribed to be 400/300 (W), a gas containingCH₂F₂/CH₃F/O₂ is prescribed, and setting temperatures of the heater areprescribed to be center/edge=35/35° C.

Lastly, referring to S7 of FIG. 5, the silicon nitride film 106 iscompletely removed (breakthrough etching). As process conditions forthis process step, a pressure of 10 (mTorr) is prescribed, the secondhigh frequency power/first high frequency power are prescribed to be200/150 (W), a gas containing CI₂ is prescribed, and settingtemperatures of the heater are prescribed to be center/edge=35/35° C.Also, O₂ ashing is performed after the breakthrough etching step. Inthis way, deposited matter may be removed. As process conditions forthis process step, a pressure of 50 (mTorr) is prescribed, the secondhigh frequency power/first high frequency power are prescribed to be750/0 (W), a gas containing O₂ is prescribed, and setting temperaturesof the heater are prescribed to be center/edge=35/35° C.

By performing the above process steps, the resist pattern may besuccessively transferred to a lower layer film, and holes having apredetermined opening width may ultimately be formed in the siliconoxide film 108.

(CD Measurement Results: Two Zones)

FIG. 6 illustrates deviations in the diameters (hereinafter referred toas “CD”, which stands for critical dimension) of holes formed on thewafer W by the above process steps. FIG. 6 illustrates the deviations inthe CD measurements of the holes in a radial direction from the wafercenter side to the wafer periphery side. The CD measurements were madeat four different measurement points arranged 90 degrees apart from eachother along a circumferential direction, and such CD measurements weremade with respect to multiple wafer positions along the radial directionfrom the wafer center side to the wafer periphery side. FIG. 6represents the result of superposing the above measurement points alonga single axis.

The horizontal axis of FIG. 6 represents a radial position of the waferwith respect to the wafer center, and the vertical axis of FIG. 6represents the CD of the holes formed at various positions. The graph onthe left side of FIG. 6 represents CD measurements of the holes farmedon the amorphous silicon film 104 after the etching step for etching theamorphous silicon film 104 illustrated by S3 of FIG. 5 has beenperformed. The graph on the right side of FIG. 6 represents CDmeasurements of the holes formed on the silicon oxide film 108 after allthe process steps up to S7 of FIG. 5 have been performed. Note that inFIG. 6, the heater 75 is divided into a center zone and an edge zone ata position approximately 130 (mm) from the wafer center.

As can be appreciated from the left side graph of FIG. 6, even at thestage of etching the amorphous silicon film 104, variations in the CD ofthe holes in the radial direction already occur at a maximum variationrange of approximately 5 (nm). Such CD variations may be attributed todeviations in the etching rate resulting from a failure to achievetemperature control uniformity across the radial direction from thewafer center to the wafer periphery.

As can be appreciated from the right side graph of FIG. 6, thedeviations in the CD of the holes become even wider after all theprocess steps of FIG. 5 are performed. Particularly, it can beappreciated that the CD of the holes become larger near the wafer center(widening near wafer center) and the CD of the holes become smaller nearthe wafer edge (narrowing near wafer edge) owing to an inadequacy in theimplementation of temperature control. The anomaly (irregularity) in theCD around the wafer center may be attributed to plasma, particularlyradicals, existing at a higher density above the wafer center region.The anomaly (irregularity) in the CD around the wafer edge may beattributed to a tendency for heat to be trapped within the wafer edgeregion and prevented from escaping outside.

Based on the above results, in the present embodiment, a region aroundthe wafer center and a region around the wafer edge where uniformtemperature control is particularly difficult are handled as anomalies,and the heater 75 is divided into a plurality of zones such thattemperature control may be separately implemented on a center zone A andan edge zone D. Further, it can be appreciated from the process resultsillustrated in FIG. 6 that the CD becomes gradually greater toward theouter periphery side even within a middle region between the center zoneA and the edge zone D. Thus, in-plane uniformity of the wafertemperature may not be achieved if this middle region is handled as onesingle zone. Accordingly, in the present embodiment, the middle regionis divided into two middle zones (i.e., inner middle zone B and outermiddle zone C). That is, in the present embodiment, the heater 75 isdivided into four zones. Note, however, that the present invention isnot limited to the above embodiment, and the middle region of the heater75 may be divided into three or more zones such that the heater 75 maybe divided into a total of five or more zones.

(Setting Temperatures of Zones)

In the following, setting temperatures of the zones are described withreference to FIG. 7. The top graph of FIG. 7 represents measurementresults of the wafer temperature in relation to the heater settingtemperature to illustrate in-plane uniformity of the wafer temperaturein exemplary cases where temperature control is implemented on theheater 75 that is divided into two zones. That is, the top graph of FIG.7 represents average values of the wafer temperature in cases where thecenter zone of the two zones is controlled to a setting temperature of60° C., and the edge zone of the two zones is controlled to a settingtemperature of 40° C., 50° C., 60° C., and 70° C. while plasma processesare performed according to the process steps illustrated in FIG. 5. Anincrease in the wafer temperature with respect to the settingtemperature may be attributed to heat input from plasma. As can beappreciated, in-plane uniformity of the wafer temperature cannot beachieved in any of the above cases. Notably, because the temperature ofthe middle zone cannot be controlled in the above cases, substantialdeviations occur at the outer periphery side of the center zone and theedge zone. Also, in the above cases, the wafer temperature at the waferedge side increases as the heater setting temperature increases owing toa tendency for heat to be trapped within the wafer edge region andprevented from escaping outside.

In view of the above results, the lower graph of FIG. 7 indicates acurved line S1 representing an estimated relationship between the heatersetting temperature and the in-plane uniformity of the wafer temperaturein a case where temperature control is implemented on the heater 75 thatis divided into four zones. Note that the diamond-shaped dots plotted inthe lower graph of FIG. 7 represent CDs of holes formed in a case wherethe heater 75 is divided into two zones and the center zone and the edgezone are controlled to setting temperatures of 60° C. and 40° C.,respectively. The square-shaped dots plotted in the lower graph of FIG.7 represent CDs of holes foamed in a case where the heater 75 is dividedinto two zones and the center zone and the edge zone are controlled tosetting temperatures of 60° C. and 50° C., respectively. In these cases,the CDs at the wafer edge tend to become smaller as the heater settingtemperature for the edge zone increases. Further, the CDs at the wafercenter side tend to become smaller as the heater setting temperature forthe center zone increases. In view of the above, the lower graph of FIG.7 indicates a curved line S2 representing an estimated relationshipbetween the heater setting temperature and the in-plane uniformity ofthe wafer temperature in a case where the center zone and the edge zoneof the heater 75 that is divided into two zones are controlled tosetting temperatures of 60° C. and 60° C., respectively.

In a case where the heater 75 is divided into four zones, and the centerzone A, the inner middle zone B, the outer middle zone C, and the edgezone D are controlled to setting temperatures of 70° C., 60° C., 70° C.,and 50° C., respectively, for example, improved in-plane uniformity ofthe wafer temperature may be achieved as illustrated by the curved lineSi. That is, in the above case, the setting temperatures for the centerzone A and the outer middle zone C are set at a higher temperature of70° C. compared to the setting temperature 60° C. for the inner middlezone B. In this way, a decrease in CD deviations and improved in-planeuniformity of the wafer temperature may be expected.

(CD Measurement Results: 4 Zones)

Based on the correlation between the setting temperatures and the CDs asdescribed above, calculations were made to obtain optimal settingtemperatures for the four zones of the heater 75 upon performing theprocess steps illustrated in FIG. 5, the optimal setting temperatureswere prescribed in a recipe, and the process steps of FIG. 5 wereperformed according to the recipe. The right side graph of FIG. 8represents process results obtained from performing the process stepsaccording to the recipe. The left side graph of FIG. 8 illustrates theprocess results in the case where the heater 75 is divided into twozones as a comparison example. As can be appreciated by comparing theleft side and right side graphs of FIG. 8, in the case where temperaturecontrol is implemented with respect to the heater 75 that is dividedinto four zones, the “widening near wafer center” and the “narrowingnear wafer edge” of the CD that occur when the heater 75 is divided intotwo zones cannot be observed thereby indicating that in-plane uniformityof the wafer temperature can be achieved. Note that the settingtemperatures of the center zone/edge zone during the etching processstep for etching the BARC film 102 in the case of implementing the2-zone temperature control were prescribed to be 60/50° C., and thesetting temperatures of the center zone/edge zone during the etchingprocess step for etching the silicon nitride film 106 in the case ofimplementing the 2-zone temperature control were prescribed to be 35/35°C. Also, the setting temperatures of the center zone/inner middlezone/outer middle zone/edge zone during the etching process step foretching the BARC film 102 in the case of implementing the 4-zonetemperature control were prescribed to be 60/45/45/43° C., and thesetting temperatures of the center zone/inner middle zone/outer middlezone/edge zone during the etching process step for etching the siliconnitride film 106 in the case of implementing the 4-zone temperaturecontrol were prescribed to be 40/45/50/50° C.

(Zone Area)

In the following, the areas of the zones are described with reference toFIGS. 9 and 10. FIGS. 9 and 10 illustrate exemplary embodiments of theheater 75 that is divided into four zones. In FIG. 9, the center zone Ahas the largest area, and the four zones have areas that becomegradually smaller from the center zone A toward the edge zone D. Thatis, the area of the heater zone at the outermost edge is the smallest.In this embodiment, temperature control may be more intricatelyperformed as the temperature control position comes closer toward theoutermost periphery, and in this way, temperature uniformity may beimproved.

In FIG. 10, the center zone A has the largest area, and the areas of thezones become smaller from the center zone A toward the outer middle zoneC. However, the area of the outer middle zone C is smaller than the edgezone D. That is, the outer middle zone C, which is second closest to theoutermost periphery, has the smallest area. In this embodiment,temperature control may be more intricately performed with respect tothe outermost middle zone positioned toward the inner side with respectto the outermost edge zone, and in this way, temperature uniformity maybe improved.

(Power Switching)

In the heater 75 having the configurations as illustrated in FIGS. 9 and10, the AC power supply 44 may be switched on/off at the middle zones(inner middle zone B and/or outer middle zone C). For example, in FIG.10, by switching on/off the power of the outer middle zone C having thesmallest zone area, temperature interference from the outer middle zoneC to its adjacent zones D and B may be prevented. In this way,temperature control may be implemented based on the correlation betweenthe temperatures of the adjacent zones D and B, and temperaturecontrollability of the wafer W may be improved in some cases. Also, byturning off the power of the heater of one or more zones, energyconsumption may be reduced.

On the other hand, the AC power supply 44 may not be switched on/off atthe center zone A and the edge zone D. This is because plasma exists ata high density around the wafer center and heat tends to be trappedwithin the outermost region of the wafer to be prevented from escapingoutside as described above. That is, the center zone A and the edge zoneD have anomalies in their temperature distributions such thattemperature control at these regions is believed to be indispensable.

As described above, in the plasma processing apparatus 1 including theheater 75 according to an embodiment of the present invention, theheater 75 arranged within or near the electrostatic chuck 40 is dividedinto at least four zones. In this way, temperature control may beseparately implemented with respect to the center zone A and theoutermost edge zone D in which anomalies occur due to plasma conditionsand/or the apparatus configuration, for example. Also, by dividing themiddle region into at least two zones, temperature control of the heatermay be more intricately conducted. As a result, in-plane uniformity ofthe wafer temperature may be achieved. Note that in the case where thesize (diameter) of the wafer is greater than or equal to 450 mm, thearea of the middle region becomes relatively large and accuratetemperature control of the middle region becomes difficult. Thus, in apreferred embodiment, the middle region may be subdivided into smallerzones according to the size of the wafer upon implementing temperaturecontrol.

[Heater Temperature Control Method]

In the present embodiment, the heater 75 is divided into four zones. Thecenter zone A and the edge zone D each have one zone arranged adjacentthereto. The middle zones B and C in the middle region each have twozones arranged adjacent thereto. The zones receive temperatureinterference from their adjacent zones. Notably, the middle zones B andC in the middle region receive temperature interference from both sides.In view of the above, more accurate temperature control may be possibleby correcting the temperature interference from the adjacent zones withrespect to the setting temperatures of the zones.

Also, note that because the surface of the electrostatic chuck 40 ispositioned above the heater 75, the surface temperature of theelectrostatic chuck 40 may not always be equal to the settingtemperatures of the zones. That is, a deviation may occur between thesurface temperature of the electrostatic chuck 40 and the temperature ofthe heater 75. Thus, more accurate temperature control may be possibleby correcting such a deviation.

In the following, a heater temperature control method is described thatinvolves correcting the temperature interference from adjacent zones,correcting the deviation between the temperature of the heater 75 andthe surface temperature of the electrostatic chuck 40, and using acorrected temperature obtained by performing the above corrections tocontrol the temperature of the heater 75 at each of the zones.

Note that in the following descriptions, as illustrated in FIG. 18,first correction values for correcting deviations of the surfacetemperature of the electrostatic chuck 40 with respect to the settingtemperatures of the center zone A, the inner middle zone B, the outermiddle zone C, and the edge zone D are represented as α₁, α₂, α₃, andα₄, respectively. Also, second correction values for correcting thetemperature interferences from zones adjacent to the center zone A, theinner middle zone B, the outer middle zone C, and the edge zone D arerepresented as β₁, β₂, β₃, and β₄, respectively. Further, thetemperature sensor 77 is used in setting up the above correction values.As illustrated in FIG. 11, in the present embodiment, the temperaturesensor 77 is arranged on the backside surface of the heater 75 withinthe inner middle zone B. However, the position of the temperature sensor77 is not limited to the above, and the temperature sensor 77 may bearranged in other zones as well. Also, the number of temperature sensors77 arranged on the heater 75 is not limited to one. In some embodiments,a plurality of temperature sensors may be arranged. In a preferredembodiment, at least three temperature sensors are arranged on acircumference of a circle. For example, in FIG. 12, four temperaturesensors 77 a, 77 b, 77 c, and 77 d are arranged on a circumference of acircle. In this way, a temperature distribution in the circumferentialdirection may be accurately detected.

[Functional Configuration of Control Device 80]

The above heater temperature control method may be executed by thecontrol device 80. In the following, a functional configuration of thecontrol device 80 is described with reference to FIG. 13, and operationsof the control device 80 are described thereafter with reference to FIG.19.

FIG. 13 illustrates the functional configuration of the control device80. The control device 80 includes an acquisition unit 81, a storageunit 83, a temperature setting unit 84, a temperature control unit 85, adetermination unit 86, and a plasma process execution unit 87.

The acquisition unit 81 continually inputs the temperature of thebackside surface of the heater 75 detected by the temperature sensor 77.In the case where a plurality of temperature sensors 77 are arranged,the acquisition unit 81 may input the temperatures detected by theplurality of temperature sensors 77.

The temperature setting unit 84 calculates the first values α₁, α₂, α₃,and α₄ for correcting the deviations of the surface temperature of theelectrostatic chuck 40 with respect to the setting temperatures of thezones, and the second values β₁β₂, β₃, and β₄ for correcting thetemperature interferences from adjacent zones with respect to thesetting temperatures of the zones, and stores the calculated correctionvalues in the storage unit 83. Note that methods for calculating thecorrection values are described in detail below.

The storage unit 83 stores a correlation between the settingtemperatures of the zones and current values to be applied to the heater75 such that the zones may be controlled to control temperatures thatare corrected based on the first values α₁, α₂, α₃, and α₄, and thesecond values β₁, β₂, β₃, and β₄. Also, the storage unit 83 may storeprocess recipes prescribing the steps and conditions of a process. Forexample, a process recipe stored in the storage unit 83 may prescribethe steps and the process conditions for executing each step of theprocess illustrated in FIG. 5.

The temperature control unit 85 adjusts the control temperature of theheater 75 with respect to each of the zones. The temperature controlunit 85 may correct the deviation of the surface temperature of theelectrostatic chuck 40 with respect to the setting temperature of eachof the zones upon adjusting the control temperature of the heater 75with respect to each of the zones. Also, the temperature control unit 85may correct the temperature interference from an adjacent zone withrespect to the setting temperature of each of the zones upon adjustingthe control temperature of the heater 75 with respect to each of thezones. The temperature control unit 85 may make one of the aboveadjustments or both of the above adjustments, for example. In making theabove adjustments, the temperature control unit 85 may adjust thecontrol temperature of the heater 75 with respect to each of the zonesbased on at least one of the first values α₁, α₂, α₃, and α₄, and thesecond values β₁, β₂, β₃, and β₄ stored in the storage unit 83. In thiscase, the temperature control unit 85 may set up the temperaturedetected by the temperature sensor 77 arranged in a given zone as asetting temperature of the corresponding zone, and calculate the currentvalue to be applied to each of the zones of the heater 75 based on thecorrelation between the setting temperatures of the zones and thecurrent values to be applied to the zones stored in the storage unit 83.

The determination unit 86 determines that it is time to replace theelectrostatic chuck 40 when at least one of the calculated currentvalues for the heater of each of the zones is less than a thresholdvalue. That is, as the heater 75 is repeatedly used, the heater 75 maybe detached from the ceramic portion of the electrostatic chuck 40 dueto thermal expansion, for example. In such case, the detached portionmay be retained at a high temperature, and as a result, the currentvalue may decrease. Note that the threshold value may be stored in thestorage unit 83, for example.

The plasma process execution unit 87 executes a plasma etching processaccording to a relevant process recipe stored in the storage unit 83.

[Correction Value Calculation]

In the following, correction functions for obtaining heater settingtemperatures Y₁, Y₂, Y₃, and Y₄ are described. Specifically, methods forcalculating the first values α₁, α₂, α₃, and α₄, and the second valuesβ₁, β₂, β₃, and β₄; and obtaining corrected heater control temperaturesusing the first values α₁, α₂, α₃, and α₄, and the second values β₁, β₂,β₃, and β₄ are described with reference to FIGS. 14-18. FIG. 14illustrates a method of calculating the correction values α₁ and β₁ withrespect to the heater setting temperature Y₁ according to the presentembodiment. FIG. 15 illustrates a method of calculating the correctionvalues α₂ and β₂ with respect to the heater setting temperature Y₂according to the present embodiment, FIG. 16 illustrates a method ofcalculating the correction values α₃ and β₃ with respect to the settingtemperature Y₃ according to the present embodiment, and FIG. 17illustrates a method of calculating the correction values α₄ and β₄ withrespect to the heater setting temperature Y₄ according to the presentembodiment. FIG. 18 illustrates corrections implemented with respect tothe setting temperatures of the zones and input current values to beapplied to the zones.

As described below, by correcting the temperature interferences fromadjacent zones and correcting the deviations of the surface temperatureof the electrostatic chuck 40 with respect to the setting temperaturesof the heater 75 to obtain corrected heater control temperatures andapplying to the heater 75 input current values corresponding to thecorrected heater control temperatures of the heater 75, the temperatureof the heater 75 may be more accurately controlled.

In the following descriptions, variables X₁, X₂, X₃, and X₄ representtarget temperatures of the center zone A, the inner middle zone B, theouter middle zone C, and the edge zone D; that is, temperatures to whichthe surface temperatures of the electrostatic chuck 40 at the abovezones should actually be controlled. Variables Y₁, Y₂, Y₃, and Y₄represent setting temperatures of the heater 75 at the center zone A,the inner middle zone B, the outer middle zone C, and the edge zone D.Variables Z₁, Z₂, and Z₃ represent adjacent temperatures as temperatureinterferences from adjacent zones. Specifically, referring to FIG. 14,the adjacent temperature interfering with the center zone A isrepresented by the variable Z₁. Referring to FIG. 15, the adjacenttemperatures interfering with the inner middle zone B are represented bythe variables Z₁ and Z₂; referring to FIG. 16, the adjacent temperaturesinterfering with the outer middle zone C are represented by thevariables Z₂ and Z₃; and referring to FIG. 17, the adjacent temperatureinterfering with the edge zone D is represented by the variable Z₃.

Note that the variables X₁, X₂, X₃, and X₄ representing the targettemperatures of the zones (surface temperature of the electrostaticchuck 40) and the variables Z₁, Z₂, and Z₃ representing the adjacenttemperatures are measured using infrared (IR) spectroscopy. Thevariables Y₁, Y₂, Y₃, and Y₄ representing setting temperatures of theheater 75 are measured using a fluorescence thermometer.

For example, with respect to the heater 75 at the center zone A, therelationship between the heater setting temperature Y₁ and the targettemperature X₁ taking into account the influence of the adjacenttemperature Z₁ may be expressed by the following formula (1):Y ₁=α₁ X ₁+β₁(Z ₁)   (1)

The graph in FIG. 14 represents the linear function expressed by theabove formula (1). If the surface temperature of the electrostatic chuck40 were actually measured, the slope α₁ will remain the same as long asthere is no influence from the adjacent temperature Z₁. In the presentexample, it is assumed that β₁(Z₁) is constant. In a case where thetemperature sensor 77 detects a sensor temperature T₁ at the backsidesurface of the center zone A, the heater setting temperature Y₁ may beset equal to the sensor temperature T₁ corresponding to an actualmeasurement value. Thus, the first correction value α₁, and the secondcorrection value β₁ may be calculated by obtaining actual measurementsof the heater setting temperature Y₁(=sensor temperature T₁) and thesurface temperature X₁, of the electrostatic chuck 40 at two or moredifferent points.

Similarly, with respect to the heater at the inner middle zone B, therelationship between the heater setting temperature Y₂ and the targettemperature X₂ taking into account the influence of the adjacenttemperatures Z₁ and Z₂ may be expressed by the following formula (2):Y ₂=α₂ X ₂+β₂(Z ₁ , Z ₂)   (2)

The graph in FIG. 15 represents the linear function expressed by theabove formula (2). It is assumed in the present example that theadjacent temperatures Z₁ and Z₂ are fixed values of a certainconceivable combination for implementing temperature control and β₁(Z₁,Z₂) is constant. In a case where the temperature sensor 77 detects asensor temperature T₂ at the backside surface of the inner middle zoneB, the heater setting temperature Y₂ may be set equal to the sensortemperature T₂ corresponding to an actual measurement value. Thus, thefirst correction value α₂ and the second correction value β₂ may becalculated by obtaining actual measurements of the heater settingtemperature Y₂(=sensor temperature T₂) and the surface temperature X₂ ofthe electrostatic chuck 40 at two or more different points.

Similarly, the first correction values α₃ and α₄, and the secondcorrection values β₃ and β₄ for controlling the temperatures at theouter middle zone C and the edge zone D may be calculated based on thefollowing formulas (3) and (4):Y ₃=α₃ X ₃+β₃(Z ₂ , Z ₃)   (3)Y ₄=α₄ X ₄+β₄(Z ₃)   (4)

Note that the linear function expressed by formula (3) is represented bythe graph of FIG. 16, and the linear function expressed by formula (4)is represented by the graph of FIG. 17. Also, it is assumed in the aboveexamples that the heater setting temperature Y₃=sensor temperature T₃,and the heater setting temperature Y₄=sensor temperature T₄.

In this way, the temperature setting unit 84 may calculate in advanceall the correction values indicated in FIG. 18 for all conceivablecombinations of temperature setting values of the adjacent zones. Thecalculated first correction values α₁, α₂, α₃, and α₄, and the secondvalues β₁, β₂, β₃, and β₄, are stored in the storage unit 83. Also, thestorage unit 83 stores a correlation between the setting temperaturesY₁, Y₂, Y₃, and Y₄ of the zones and current values I₁, I₂, I₃, and I₄ tobe applied to the zones of the heater 75 such that the heatertemperatures at the zones may be equal to the control temperaturescalculated for the zones based on the first correction values α₁, α₂,α₃, and α₄, and the second correction values β₁, β₂, β₃, and β₄.

According to the above correction value calculation methods, relativerelationships with respect to temperature variations between adjacentzones are determined beforehand, and the temperature of one zone isactually measured and the measured temperature is used as a basetemperature to obtain input current values to be applied to the zones ofthe heater 75. In this way, correction-implemented temperature controlmay be performed on the zones of the heater 75.

Note that in the above descriptions, for example, with respect to theheater 75 at the inner middle zone B, the relationship is approximatedusing β₂(Z₁, Z₂) as the influence from adjacent zones. However,correction accuracy may be further improved by additionally taking intoaccount influences from other zones that are not directly adjacent tothe zone of interest. For example, with respect to the heater 75 at theinner middle zone B, the relationship may be approximated taking intoaccount influences not only from the center zone A and the outer middlezone C but also the edge zone D using β₂(Z₁, Z₂, Z₃) (see formula (6)indicated below). In this way, correction accuracy may be furtherimproved. Similarly, correction values may be calculated in advancetaking into account influences not only from adjacent zones but otherremote zones using formulas (5)-(8) indicated below.Y ₁=α₁ X ₁+β₁(Z ₁ , Z ₂ , Z ₃)   (5)Y ₂=α₂ X ₂+β₂(Z ₁ , Z ₂ , Z ₃)   (6)Y ₃=α₃ X ₃+β₃(Z ₁ , Z ₂ , Z ₃)   (7)Y ₄=α₄ X ₄+β₄(Z ₁ , Z ₂ , Z ₃)   (8)

Further, in a case where the power of the outer middle zone C is turnedoff, temperature interference from the outer middle zone C may bedisregarded. Accordingly, the relationship between the settingtemperatures of the zones of the heater 75 and the target temperaturesmay be expressed by the following foLmulas (9)-(11):Y ₁=α₁ X ₁+β₁(Z ₁ , Z ₃)   (9)Y ₂=α₂ X ₂+β₂(Z ₁ , Z ₃)   (10)Y ₄=α₄ X ₄+β₄(Z ₁ , Z ₃)   (11)

[Control Device Operations]

Lastly, operations of the control device 80; namely, temperature controloperations executed by the control device 80 are described below withreference to the flowchart of FIG. 19. Note that in the present example,Z represents the adjacent temperature of an adjacent zone. As describedabove, the first correction values α₁-α₄ and the second correctionvalues β₁-β₄ for the zones are calculated in advance and stored in thestorage unit 83. Also, the correlation between the corrected heatersetting temperatures Y₁-Y₄ and the input current values I₁-I₄ is storedin the storage unit 83.

When the present process is started, first, the acquisition unit 81acquires the sensor temperature T₂ detected by the temperature sensor 77that is arranged at the inner middle zone B (step S100). Then, thetemperature setting unit 84 uses the sensor temperature T₂ as a basetemperature, assigns the sensor temperature T₂ to the heater settingtemperature Y₂ of formula (2), assigns a target value to the targettemperature X₂ of formula (2), and calculates the adjacent temperaturesZ of adjacent zones (step S102).Y ₂=α₂ X ₂+β₂(Z ₁ , Z ₂)   (2)

Then, using formulas (1), (3), and (4), the temperature setting unit 84assigns target values to the target temperatures X₁, X₃, and X₄, andassigns the adjacent temperatures Z of the adjacent zones to calculatethe heater setting temperatures Y₁, Y₃, and Y₄ (step S104).Y ₁=α₁ X ₁+β₁(Z ₁)   (1)Y ₃=α₃ X ₃+β₃(Z ₂ , Z ₃)   (3)Y ₄=α₄ X ₄+β₄(Z ₃)   (4)

Then, based on the correlation between the setting temperatures of thezones and the current values I stored in the storage unit 83, thetemperature control unit 85 calculates the heater input current valuesI₁, I₂, I₃, and I₄ corresponding to the heater setting temperatures Y₁,Y₂, Y₃, and Y₄, and applies the heater input current values I₁, I₂, I₃,and I₄ to the corresponding zones of the heater 75 to thereby controlthe heater temperatures at the corresponding zones (step S106).

Then, the determination unit 86 determines whether any of the heaterinput current values I₁, I₂, I₃, and I₄ is less than a predeterminedthreshold value. Upon determining that at least one of the heater inputcurrent values I₁, I₂, I₃, and I₄ is less than the predeterminedthreshold value, the determination unit 86 determines that it is time toreplace the electrostatic chuck 40 (step S108) after which the presentprocess is ended. When the determination unit 86 determines that none ofthe heat input current values I₁, I₂, I₃, and I₄ is less than thepredetermined threshold value, the present process is immediately ended.

[Effects]

As described above, in the plasma processing apparatus 1 including theheater 75 according to an embodiment of the present invention, theheater 75 arranged within or near the electrostatic chuck 40 is dividedinto at least four zones. In this way, temperature control may beseparately implemented with respect to the center zone A and theoutermost edge zone D where anomalies are likely to occur due to plasmaconditions or the apparatus configuration. Also, more intricatetemperature control of the heater 75 may be enabled by dividing themiddle region into at least two zones. As a result, in-plane uniformityof the wafer temperature may be achieved.

Also, the zones receive temperature interference from adjacent zones.The middle zones are particularly susceptible to large temperatureinterferences. Accordingly, in a temperature control method that may beimplemented by the plasma processing apparatus 1 of the presentembodiment, correction may be implemented on temperature interferencesfrom adjacent zones with respect to the setting temperatures of thezones. Also, the setting temperatures of the zones may incorporatecorrections on deviations in the surface temperature of theelectrostatic chuck 40 arranged above the heater 75. In this way, highlyaccurate temperature control may be enabled.

Although illustrative embodiments of the present invention have beendescribed above with reference to the accompanying drawings, the presentinvention is not limited to these embodiments. That is, numerousvariations and modifications will readily occur to those skilled in theart, and the present invention includes all such variations andmodifications that may be made without departing from the scope of thepresent invention.

For example, although a plasma etching process is described above as anexample of a plasma process that may be executed by a plasma processingapparatus, the present invention is not limited to plasma etching, butmay also be applied to plasma processing apparatuses that perform plasmachemical vapor deposition (CVD) for forming a thin film on a waferthrough CVD, plasma oxidation, plasma nitridization, sputtering, oraching, for example.

Also, a plasma processing apparatus according to the present inventionis not limited to a capacitively coupled plasma processing apparatusthat generates capacitively coupled plasma (CCP) by discharging a highfrequency generated between parallel plate electrodes within a chamber.For example, the present invention may also be applied to an inductivelycoupled plasma processing apparatus that has an antenna arranged on ornear a chamber and is configured to generate inductively coupled plasma(ICP) under a high frequency induction field, or a microwave plasmaprocessing apparatus that generates a plasma wave using microwave power.

Also, the workpiece subject to a plasma process in the present inventionis not limited to a semiconductor wafer but may be a large substrate fora flat panel display (FPD), an electroluminescence (EL) element, or asubstrate for a solar battery, for example.

Also, according to an embodiment of the present invention, the heatermay be arranged such that the center zone and the at least two middlezones have areas that become smaller toward the outer periphery side,and an outermost middle zone of the at least two middle zones has anarea that is smaller than an area of the edge zone arranged at the outerperiphery side of the outeLinost middle zone.

Also, in another embodiment of the present invention, the heater may bearranged such that the center zone, the at least two middle zones, andthe edge zone have areas that become smaller toward the outer peripheryside.

Also, the temperature control unit may turn off the heater of theoutermost middle zone and adjust the control temperature of the heaterof the zones other than the outermost middle zone.

Also, the temperature control unit may correct a deviation of a surfacetemperature of the electrostatic chuck with respect to a settingtemperature of each of the zones upon adjusting the control temperatureof the heater with respect to each of the zones.

Also, the temperature control unit may correct a temperatureinterference from an adjacent zone with respect to a setting temperatureof each of the zones upon adjusting the control temperature of theheater with respect to each of the zones.

Also, a plasma processing apparatus according to an embodiment of thepresent invention may further include a temperature setting unitconfigured to set up a first correction value for correcting a deviationof a surface temperature of the electrostatic chuck with respect to thesetting temperature of each of the zones and a second correction valuefor correcting the temperature interference from the adjacent zone withrespect to the setting temperature of each of the zones. The temperaturecontrol unit may adjust the control temperature of the heater withrespect to each of the zones based on the first correction value and thesecond correction value.

Also, the temperature setting unit may store in advance in a storageunit a correlation between the setting temperature of each of the zonesand a current value to be applied to the heater of each of the zones tocontrol the heater to the control temperature that is calculated withrespect to each of the zones based on the first correction value and thesecond correction value. The temperature control unit may acquire atemperature detected by a temperature sensor arranged in at least onezone of the plurality of zones, set up the acquired temperature as asetting temperature of the at least one zone, and calculate the currentvalue to be applied to the heater of each of the zones based on thesetting temperature of the at least one zone and the correlation storedin the storage unit.

Also, a plasma processing apparatus according to an embodiment of thepresent invention may further include a determination unit configured todetermine that a time for replacement of the electrostatic chuck hasbeen reached when at least one current value of the calculated currentvalue for the heater of each of the zones is less than a predeteLminedthreshold value.

Also, at least three temperature sensors may be arranged along acircumference of a circle within the at least one zone.

Also, a plasma processing apparatus according to an embodiment of thepresent invention may further include a coolant path arranged oppositethe heater, which is arranged within or near the mounting table; and achiller device configured to circulate a coolant within the coolantpath.

Also, the mounting table may hold a workpiece having a diameter greaterthan or equal to 450 mm, and the middle zones of the heater may beconcentrically divided into at least three zones.

The present application is based on and claims the benefit of priorityof Japanese Patent Application No. 2012-005590 filed on Jan. 13, 2012,and U.S. Provisional Application No. 61/587706 filed on Jan. 18, 2012,the entire contents of which are herein incorporated by reference.

DESCRIPTION OF THE REFERENCE NUMERALS

-   1 plasma processing apparatus-   10 chamber-   12 mounting table (lower electrode)-   31 first high frequency power supply-   32 second high frequency power supply-   38 shower head (upper electrode)-   40 electrostatic chuck-   44AC power supply-   62 gas supply source-   70 coolant path-   71 chiller unit-   75 heater-   77 temperature sensor-   80 control device-   81 acquisition unit-   83 storage unit-   84 temperature setting unit-   85 temperature control unit-   86 determination unit-   87 plasma process execution unit-   100 photoresist film-   102 BARC film-   104 α-Si film-   106 SiN film-   108 SiO₂ film-   A center zone-   B inner middle zone-   C outer middle zone-   D edge zone

The invention claimed is:
 1. A method for controlling a temperature of aheater arranged in a plasma processing apparatus that is configured toconvert a gas into plasma using a high frequency power and performplasma processing on a workpiece with the plasma, wherein the plasmaprocessing apparatus includes a processing chamber that can bedepressurized, a mounting table that is arranged within the processingchamber and that is configured to hold the workpiece, an electrostaticchuck that is arranged on the mounting table and that is configured toelectrostatically attract the workpiece by applying a voltage to a chuckelectrode, a heater arranged within or near the electrostatic chuck, theheater being divided into a plurality of concentric zones including acircular center zone, a plurality of intermediate zones arranged at anouter peripheral side of the center zone, and an edge zone arranged atan outer peripheral side of an outermost intermediate zone of theplurality of intermediate zones, the heater temperature control methodcomprising: adjusting a control temperature of the heater with respectto each of the plurality of zones of the heater; and correcting atemperature interference from an adjacent zone of each of the zones withrespect to a setting temperature of each of the zones upon adjusting thecontrol temperature of the heater with respect to each of the zones. 2.The temperature control method according to claim 1, further comprising:setting a first correction value to correct for a deviation of a surfacetemperature of the electrostatic chuck with respect to the settingtemperature of each of the zones; and setting a second correction valueto correct for the temperature interference from the adjacent zone ofeach of the zones with respect to the setting temperature of each of thezones; wherein the control temperature of the heater with respect toeach of the zones is adjusted based on the first correction value andthe second correction value.
 3. The temperature control method accordingto claim 2, wherein the method further comprises: storing in a memory ofthe plasma processing apparatus, in advance, a correlation between thesetting temperature of each of the zones and a current value to beapplied to each of the zones of the heater to control the temperature ofeach of the zones of the heater to the control temperature that iscalculated with respect to each of the zones, based on the firstcorrection value and the second correction value; acquiring atemperature detected by a temperature sensor arranged in at least onezone of the plurality of zones; setting the acquired temperature as asetting temperature of the at least one zone; and calculating a currentvalue to be applied to the heater of each of the zones of the heaterbased on the setting temperature of the at least one zone, the storedcurrent value to be applied to each of the zones of the heater and thestored correlation between the setting temperature of each of the zones.4. The temperature control method according to claim 3, wherein themethod further comprises: comparing the calculated current value foreach of the zones of the heater with a predetermined threshold value;and determining that the electrostatic chuck is due for replacement whenat least one current value of the calculated current value for each ofthe zones of the heater is below the predetermined threshold value. 5.The temperature control method according to claim 1, wherein the heateris arranged such that the center zone and the plurality of intermediatezones have areas that become smaller toward the outer periphery side,and an area of the outermost intermediate zone of the plurality ofintermediate zones is smaller than an area of the edge zone, and themethod further comprises: turning off a power of the outermostintermediate zone; and adjusting the control temperature of each of thezones other than the outermost intermediate zone.